Equipment for resistance bitt-welding

ABSTRACT

A resistance butt-welding equipment for welding casing pipes above the well head into a string and subsequent running the string into the well, comprising a grip whose maximum overal dimensions do not exceed the outer diameters of the casing pipe. This allows the welded casing string to be lowered through a welding machine thereby achieving higher production efficiency.

v United States Patent Sakharnov et al.

[ 11 1 3,836,746 Sept. 17, 1974 [54] EQUIPMENT FOR RESISTANCE [56] References Cited BUT-WELDING UNITED STATES PATENTS [76] Inventors: Vasily Alexeevich Sakharnov, bulvar 2,687,322 8/1954 Amrhein 269/52 X Likhacheua, 3, kv, 64; Alfred 2,777,048 l/l957 Kocks 219/161 Nikolaevich popov ulitsa Sholom 3,341,684 9/1967 Paton et al 219/101 Aleikhema 5/2 10 Vladimir 3,538,295 11/1970 Paton et al 219/101 Ivanovich Tishura, ulitsa Nikolaya Gaitsana 6, kv. 7; Boris Alanasievich 'f Truhe Galyan, ulitsa Lenina 88/92, kv. Asmmm. -N- llfarkamp y no; Jury valentinovich skulsky, Attorney, Agent, or Firm-Eric H. Waters ulitsa Bastionnaya l0, kv. 30, all of Kiev, USSR [57] ABSTRACT A resistance butt-welding equipment for welding cas- [22] Filed June 1973 ing pipes above the well head into a string and subse- [21] Appl. N0.: 366,211 quent'running the string into the well, comprising a grip whose maximum overal dimensions do not exceed the outer diameters of the casing pipe. This allows the ((jil. Mil/12315311?l welded casing string to be lowered through a welding [58] 4 107 160 machine thereby achieving higher production effi- 10 Claims, 8 Drawing Figures 3 4 I IV PATENTEDSEPITIW 3.836 746 SHEET 1 0F 5 PATENTEBSEPI H974 WEI 3 BF 5 PATENTEDSEP] 71914 SHEET 5 [IF 5 1 EQUIPMENT FOR RESISTANCE BIIT-WELDING string and subsequent running the latter into the well.

The principal component .units ,of these outfits are machines for resistance butt-welding of casing pipes and a grip to deliver the casing pipes into the welding machine and to run the welded casing string into the well, the grip being connected to a mechanism for vertical displacement thereof.

However, existing equipment does not allow full utilization of the advantages provided by the highly productive resistance butt-welding-process. This, first of all, should be referred to pipe grips, used on drilling rigs, to deliver pipes to be welded into the welding machine and subsequently to lower an extended casing string.

These ips are pe itiohe ut de th Pi e in Welded t ing t melee heeeseeree ou th space n h oi ze e f r pa s n h s ir t ether with e t n unt t to e d of the string s nosioned e th we in l l- In other words, a necessity arises to move the welding machine away from the welding zone. Moving away and bringing in the welding machine reduce labour prot vi y n .lewe ing th cas ng st ing. a a s requ r ene ulky ech n sm e ran f ri g the w dins ma in T h d sign o th outfit oh th who is thus made substantially more complicated.

The existing outfits or machines for connecting casing pipes into a casing string employ two types of resistance butt-welding machines. The first type includes machines with side charging and discharging of the casing pipes being welded. in these machines, clamping of the pipes is performed by means of two jaws, prism-like in shape, moving towards each other, and therefore from the engineering point of view it is impossible to distribute the clamping force uniformly over the perimeters of the pipes being clamped, which materially disturbs the quality of centering and consequently the quality of welding.

This is especially evident in welding low-rigidity pipes thin-walled large diameter pipes. To allow'for passing the grip positioned outside the pipes together with the casing string, the welding machines of this type have to be moved away from the welding zone by means of pecial mechanisms in the direction perpendicular to the well axis. This moving-away action cuts labour productivity.

Highest quality of welding is achieved by using weld: ing machines of the so-called through-passing type. These machines include non-split housings embracing I the pipes being welded, and the casing-pipe clamping mechanisms ensure uniform distribution of the clamping force over the entire perimeters of the pipes being clamped.

However, toclear out the space to pass the external 's p o eth with h eas n String ei run down.

these machines need to be installed on special-type telescopic hoists to, displace the machine along the axis of the casing string. Additional mechanisms, needed to move away and bring in the welding machine in this case, also reduce labour productivity. I

In addition, after installing the welding machine on the telescopic hoist, the level of welding'occurs substantially on an elevated level, above thedrilling rig floor, which brings much discomfort to the operator from the safety point of view.

The primary object of the invention is to provide an equipment for resistance butt-welding of casing pipes above the well head into a string and subsequent run ning it into the well which ensures higher labour productivity as compared with known structures of this ype- Another object of the invention is to provide an equipment for resistance butt-welding which does not require the use of additional devices and technological operations in bringing in and moving away th welding machine from the welding joint location.

One more object of the present invention is ,to pro.- -vide an equipment which permits clearing off the working space in the drilling rig.

Still another object of the invention is to provide an equipment which provides higher operation safety.

These and other objects are achieved due to the provision of an equipment for resistance butt-welding of casing pipes, above a well head, and subsequent runningthe resulting casing string into the well, which comprises a welding machine .of the type adapted to be passed through, incorporating a non-split housing embracing a casing string and having mechanisms for clamping the ends of the pipes being welded, and a grip positioned in coaxial relationship with the welding machine to deliver the casing pipes into this welding machine, to run the welded casing string into the well, and connected to a mechanism for vertical displacement of the axis along the axis of the well, wherein the grip in its maximum crosssectional dimensions does not exceed the outer diameters of the casing pipes, to permit running the casing string through the non-split housin of the welding machine, the latter being stationarily installed above the well.

The design of a grip, whose overall dimensions are not in excess of the outer diameter of a pipe being welded, permits vertical displacement of the grip together with the string being lowered, without need for additional operations, such as for moving the welding machine relative to the welding zone. This, in turn, allows for higher labour productivity and for the application of a stationarily installed machine of the described type, yielding higher quality of welding as compared with other machines of a similar type. Apart from that, the welding machine operating conditions and the safety are improved.

Another feature of the present invention is that the pipe grip comprises two coaxial systems with possible displacement in relation to preferably each other, with one system taking the shape of a hollow rod connected to the vertical displacement mechanism, one end of the rod being given the shape of a cylinder, while the other end has at least two, namely upper and lower, wedgeline steps, with each of them made as a truncated pyramid, with a longitudinal axis coinciding with the ,longitudinal axis of the rod, and with the apex facing the cylindrical end portion of the rod, whereas the other system comprises wedge-like clamping jaws installed on eac a e o th pyram d with pessibili y o displacement along the face, ensuring radial displacement in the cross-sectional planes of the casing pipes until the clamping jaws rest against the inner surfaces of the casing pipes.

Introduction of wedge-like steps opens way to utilization of the wedge-joint effect in clamping the pipes, that is to obtain a clamping force proportional to the weight of the pipes. A number of wedge like steps is selected with respect to the weight of the casing string being clamped, with due consideration of the permissible stresses in the pipe walls at the place of their contact with the working surfaces of the clamping jaws. The hollow rod permits a rope to be placed inside thereof for an additional tool to be secured to its end, such as a dross remove.

It is recommended that the wedge-like jaws are adapted to be displaced along guides made on the faces of pyramids of the each wedge-like step. These guides are instrumental in the strict orientation of the working surfaces of the clamping jaws in relation to the inner surfaces of the pipes being clamped, which improves the clamping conditions and ensures constant contact between the jaws and the faces of the pyramids.

It is also expedient to match the shape of the working surfaces of the clamping jaws to the shape of the inner surfaces of the casing pipesand to provide teeth directed perpendicular to the axis of the casing pipes.

The conformity between the working surfaces of the clamping jaws and the inner surfaces of the casing pipes assists in a uniform distribution of the clamping force, while the teeth on the working surfaces of the clamping jaws, and directed perpendicular to the pipe axis, increase the coefficient of friction in the contacting surfaces, and consequently the clamping force as well.

It is technologically advisableto position the jaws of each step oppositely each other, that is in a vertical alignment, rigidly connecting them by mechanisms for adjusting the distance between them, to correct discrepancies which may occur in the manufacture of the clamping jaws and the wedge-like steps of the rod. The introduction of correcting mechanisms between the oppositely located jaws of each step contributes toward uniform distribution of the clamping force between all jaws of all steps, to obviate maximum stresses caused in the pipes being clamped.

It is further expedient to have the mechanism for adjusting the distance between the jaws in the form of two screws, with one of them of having a right-hand thread and being connected to one of the clamping jaws, and the other having a left-hand thread and. being connected to the opposite jaw, the screws being interconnected by a nut having corresponding threads. This design of the mechanism gives a ready and reliable adjustment of the distance between the jaws, while being simple to manufacture.

It is recommended to provide the cylindrical end of the rod with a sleeve liable to axial displacement thereof and connected to each clamping jaw of the upper wedge-like step by means of a two-link mechanism. The two-link mechanism connecting each upper jaw to the sleeve frees the jaws from radial displacement relative to the sleeve. At the sametime the jaws, together with the sleeve, are able of cooperative displacement along the axis of the rod, which is required in clamping or releasing the pipes.

Another additional feature of the invention is that the outer surface of the sleeve. is threaded, and this thread carries a spacer nut with a spherical surface.

In accordance with another feature of the equipment, each clamping jaw of the upper wedge-like step has mounted thereon a pivoted, spring-loaded lever for preliminary clamping of the casing pipes, having on the end thereof opposite to the pivoted joint aspherical rubbed surface facing the inner surfaces of the casing pipes, and a wedge-like surface of the jaw, cooperating with the spherical surface of the spacer nut. The'springloaded lever and the spacer nut permit preliminary clamping of the pipes, and only after this action can the main clamping operation be effected.

The preferred embodiment of the invention admits of other design modifications of the :equipment, which may be so constructed that each face of at least one of the wedge-like steps of the rod carries a spring-loaded pin-type detent cooperating'with a seat made in the corresponding clamping jaw located in its extreme upper position.

The spring-loaded detent is capable of locking the clamping jaws in the extreme upper position, which in turn defines a clearance between. the working surfaces of the clamping jaws and the inner surfaces of the pipes, to enable the internal grip to be introduced into or extracted from the pipes.

Other objects and advantages will become more fully apparent from a detailed description of an actual, exemplary embodiment with, reference to the accompanying drawings, in which:

FIG. 1 is a somewhat schematic general view of the equipment for resistance butt-welding of casing pipes according to the invention;

FIG. 2 is a section takenalong the line II II of FIG.

1; FIG. 3 is a section taken along the line III III of FIG. 2;

FIG. 4 is a section taken along line IV IV of FIG.

FIG. 6 is a section taken along line VI VI of FIG. 4;

FIG. 7 is a section taken along line VII VII of FIG. 4; and

FIG. 8 is a section taken along line VIII VIII of FIG. 4..

The equipment for resistance butt-welding of casing pipes above the well head into a casing string and subsequent running the string into the well comprises a welding machine 1 (FIG. 1) of the so-called passthrough type and a grip 2 mounted in coaxial relationship with the welding machine I to deliver casing pipes 3 into the welding machine 1 and subsequently to run the welded casing string 4 into the well, and connected to a mechanism 5 for its vertical displacement along the axis of the well.

The welding machine 1 is stationarily installed above the well on a rotary table 6 of a drilling rig 7. The mechanism 5 for vertical displacement of the grip 2 takes the fonn of a tackle system incorporated in the drilling rig The welding machine (FIGS. 2 and 3) incorporates lower and upper non-split housings 8 and 9 embracing the casing string 4. In .the following description the housing 8 will be referred to as lower? because it faces the well, and the housing-9 upper. Installed inside each housing 8 and 9 with possible turning about the longitudinal'axis of the machine 1 is a holder 10.

r10. 5 isa section taken along line v v of FIG. 4;

On each housing 8, 9 of' the welding machine 1 there are two pivotally installed cylinders 11 Cylinders ll belonging to the lower housing 8. serve to clamp the casing string, while cylinders 11 belonging to the upper housing 9 serve for clampingthe casing pipes in extending the welded casing string. Rods 12 of cylinders 11 are connected by means of hinges 13 to corresponding holders I Each housing 8,- 9 incorporates, clamping currentfeeding shoes 14 given a freedom of radial displacement and having wedge-like surfaces 15 and. surfaces 16. In accordance with anumber-of clamping shoes14,v

adapted to move towards'each other'the casing. string.

4 and the pipe 3'inthe course of welding; Rods 22 of cylinders 2l'are rigidly connectedto the. lower housing 8. Installed on rods 22 are clamping plates 23. Positioned between the clamping plate 23 and the lower housing 8, in coaxial relationship with thewelding mas chine l, is a circular welding transformer 24 connected through busbars 25 with clamping current-feeding shoes 14. The lower housings of the machine isstationarily fixed on the rotary table 6'.

The grip 2' illustrated inFIG. 4, to deliver the casing.

pipes into the welding. machine and subsequently to lower down the welded casing string, comprisestwo systems which .are in coaxial relationship, with possible relative displacement. One'of-these system represents.

a hollow rod 26 (FIG. 5") whose one end has a cylindrical surface 27 (FIG. 4), while theotherend includes two wedge-like steps 28.

An exact number of:wedge-like steps 28 is dictated by the design requirements depending on the weight of the casing string, the casing pipe wall thickness and the material, i.e., on the mechanical and geometric characteristics of the casing string. Each step 28 takes the form of a truncated pyramid with its. longitudinal. axis coinciding with the longitudinal axis of the rod 26, and with the apex facing. the cylindrical end of the rod 26, which by means of an adapterelement 29 is connected to the mechanism Sfor vertical displacement...

The other system comprises wedge-like clamping.

jaws 30 (FIG. 5) installed on each face of said pyramid of each step 28, with possible displacement thereof along the face to ensure radial displacement of the jaw in-the cross-sectional plane of the casing pipe 3 until clamping jaws 30 come. into contact with the inner surface of the casing pipe 3. I i I The configuration ofthe working surface of the wedge-like clamping jaws 30 matches the configuration of theinner surface of the casing pipe 3 and is-provided with teeth 31 (FIG. 4) directed perpendicular to the longitudinal axis of the casing pipe 3. Theteeth '31 increase the frictionalforce between the working. surface of the jaws 30 and the pipe 3 when the latter is being. clamped. The faces of the pyramidsof the wedge-like steps 28 have guides 32 (FIG. 6);which-, with wedgelike clamping jaws 30 displaced therealon'g, ensure proper orientation of the latter jaws relative to the inner surface. of the casing pipe 3.

Wedge-like clamping jawsg30 of each step, positioned oppositely to each other in a vertical direction are rigidly interconnected by mechanisms for adjusting the distance between them. These adjusting. mechanisms are instrumental in eliminating the effects of discrepancies occured in the manufacture of clamping jaws 30 and the wedge-like steps of rod 26, which ultimately helps' achieve uniform distribution of the clamping force among all jaws 30 and reduce maximum stresses occurring. in the pipe 3 or the casing string 4.

The mechanism for adjusting the distance between jaws 30 is made in the form of two screws 33 (FIG. 4) and 34 (FIG. 5). The'screw 33 has a right-hand-thread and is connected to one of the clamping jaws30, while the other screw 34 has a left-hand thread and is connected to the opposite jaw 30; with thisarrangement, screws 33 and 34 are interconnected by a nut 35 threaded in compliance with the screws.

The cylindrical surface 27 of the hollow rod 26 is provided with a sleeve 36 (FIG. 7) connected to each clamping jaw 30 of the upper step (next to the cylindrical end of the rod) by means of atwo-link mechanism 37, enabling the clamping jaws 30 to move relative to the axis of the rod 26 and, at the same time, to move longitudinally relative to the axis of the rod 26' together with the sleeve 36. I

The outer surface of the sleeve 36 is threaded to mount thereon a spacer nut 38 (FIG. 4 having an outer spherical surface 39. Each clamping jaw 39 of the upper step 28 carries by means of a lever 40 (FIG. 8),

a spring-loaded lver 41 having on its'end opposite to the hinge 40 a spherical ribbed surface 42" (FIG. 4) facing the inner surface of the casing pipe 4, anda wedgelike surface 43 facing the spherical surface 39 of the nut 38 and cooperating with the latter in thepreliminary clamping of the pipes.

A spring 44 (FIG. 8) of the lever 41 tends to separate the spherical ribbed surface of the lever4l from the inner wall of the pipe, thus disconnecting the spherical ribbed surface 42 from the inner surface of the pipe to remove the grip from the pipes.

Mounted in each face of one of the wedge-like steps 28 of the rod 26 is a spring-loaded pin-type detent 45 (FIG. 4) provided with a spring 46 and cooperating with a seat 47 made in the corresponding clamping jaw 30 in its extreme upper position, to enable the grip to be inserted in or removed from the pipe.

A number of pin-type detents are steps provided with them is determined in accordance with the design depending principally on the weightand size of the movable components of the grip.

Thus,.the equipment according-to the present invention, is provided with a grip 2 whose maximum overall dimensions in its cross'section do not exceed the outer .diameter d (FIG. 1) of thecasing pipe 3,to permitaccommodation of the grip 2 inside the casing pipe 3. This in turn makes it possible to install on the drilling rig a welding machine of the pass-through type with the aim to improve the quality of welding, avoid the application of additional devices and/technological processes in bringing the machine in.and 'away, which otherwise reduce labour productivity, encumber the work- 7 ing space in the drilling rig and impair operational safety.

The equipment operates as follows. The casing string 4 welded up to a certain length has been run into the well and clamped in the rotary table 6 of the drilling rig 7. At this time, the upper end of the casing string is at the welding level. Now the grip 2 is being prepared for introduction into one of casing pipes 3 to be welded to the casing string 4 which is positioned on the drilling rig 7 in a vertical or inclined stack.

For this purpose, the spacer nut 38 is turned to let springs 44 move levers 41 through a maximum value towards the longitudinal axis of the grip. Then, wedgelike clamping jaws 30 are displaced along guides 32 of wedge-like steps 28 to the extreme upper position until springs 46 get released to push pin-type detents 45 into seats 47. Jaws 30, while moving along the guides of wedge-like steps 28 approach the longitudinal axis of the grip 2 to establish the requirement clearance between the teeth 31 of its working surfaces and the inner surfaces of the casing pipes. During their displacement, jaws 30, acting through two-like mechanisms 37, force the sleeve 36 to move to the upper positions.

The mechanism for vertical displacement is now applied to introduce the grip 2 into the next casing pipe 3 and the grip is fixed inside the pipe. To this aim, the nut 38 is turned to act with its spherical surface 39 on the wedge-like surfaces 43 of the levers 41. This makes the levers 41 turn around the joints 40 which, by depressing springs 44, press with their spherical ribbed surfaces 42 against the inner surface of the pipe 3 with a force proportional to the force applied to the nut 38.

Then, through the mechanism 5, action is imposed via the adapter element 29 on the rod 26 to raise the latter. Under the weight of the pipe 3 transmitted to the grips 2 through levers 41 pressed against the pipe, springs 46 are compressed, detents 45 come out of their seats 47, and relative displacement takes place between the rod 26 and the wedge-like clamping jaws until the latter are pressed against the inner surface of the pipe 3. Y

When this occurs, two-link mechanisms 37 render no obstacle to the radial displacement of jaws 30 relative to the longitudinal axis of the grip 2. Turning of the lever 41 by a small angle around the joint 40, due to the displacement of jaws 30, practically causes no reduction in the force of preliminary fixing (preliminary clamping) of the grip 2 inside the pipe because the working surface 42 of the lever 41 is spherical in shape.

After resting the jaws 30 against the inner surface of I force of clamping the pipe is proportional to its weight and depends on the coefficient of friction between the jaws 30 and the inner surface of the pipe and; also on the angling of the wedge-like steps and the internal frictional forces.

The casing pipe 3 clamped by the grip 2 is now inserted in the upper housing 9 of the welding machine 1 until the lower end of the pipe is at the welding level. The casing pipe 3 and the casing string 4 are clamped in the welding machine 1. This is done by admitting oil into spaces A (FIG. 3) of cylinders 11 of the lower housing 8 and the upper housing 9. Rods 12 of cylinders 11 force their action through hinges13 on holders tively with the outer surfaces of the casing pipe and the casing string. The welding transformer 24 is switched on and the welding process is carried out by bringing the housing 9 together, with the casing pipe 3 clamped therein towards the casing 8, together with the "casing string 4 clamped therein, by delivering oil to space B (FIG. 2) of cylinders 11. The housing 9 is displaced along rods 22.

On completion of the welding process, the casing pipe and the casing string welded thereto are released. This is obtained by supplying oil to space C (FIG. 3) of cylinders 11 of housing 8 and 9. Rods 12 via hinges 13 impose action on the holders 10 to turn the latter counter-clockwise. Holders 10 through their protrusions 20act on the arms of double-arm levers 18 which when turning around axles 17 act with their other arms on the surfaces 16 of shoes 14 to force the latter away from the center of the machine.

Then, oil is admitted to space D (FIG. 2) of cylinders 21 to part housings 8 and 9, that is to bring the welding machine to the initial position, ready for the next welding operation. The casing string lengthened after welding to'it another casing pipe is freed from clamping in the rotary table 6. And this loads the grip 2 with the full weight of the casing string. Using the mechanism 5, the string is run into the well until the upper end thereof is at the welding level; afterwards the casing string is again clamped in the rotary table 6.

I With the help of the mechanism 5, the rod 26 is lowered to a moment when detents 45 enter seats 47 due to the action of springs 46. At this time all the remaining components are in the vertically fixed position relative to the pipe at the expense of the force of clamping the surfaces 42 of levers 41 against the inner walls of the pipe. When the rod 26 is moved down, the jaws 30 are displaced radially to establish a clearance between their working surfaces and the inner walls of the pipe.

Then by turning the spacer nut 38 of the grip 2 the levers 41 are released from contact by their surfaces 42 i with the inner walls of the pipe, whereupon the grip 2 is pulled out of the casing string by means of the mechanism 5. A new casing pipe is clamped, then brought into the welding machine, and the procedure is repeated.

Discrepancies occurring in the manufacture of wedge-like steps 28 and wedge-like clamping jaws 30, affecting the uniform contact of the latter with the inner walls of the pipe, are eliminated by turning the nuts 35 in the appropriate direction. This consists in that the nuts 35 cooperating with screws 33 and 34 force the opposite jaws 30 to separate or to approach.

What is claimed is:

1. An equipment for resistance butt-welding of casing pipes above a well head into a casing string and subsequent running the string into the well, comprising: a welding machine of the type adapted to pass through and installed in a stationary manner above the well; a grip to bring the pipes into said welding machine and to run a welded casing string into the well, located coaxially to said welding machine, a mechanism for vertical displacement of said grip along the axis of the well; said welding machine including mechanisms for clamping the ends of the pipes being welded, and a non-split housing embracing the string and connected to said clamping mechanism; said grip having maximum overall cross-section dimensions that do not exceed the outer diameters of the pipes, to permit the welded string to be lowered through said housing of the welding machine.

2. The equipment as defined in claim 1, wherein said grip includes two systems positioned coaxially for possible relative displacement, one system representing a hollow rod connected to said displacement mechanism, whose one end has a cylindrical surface, while the other end thereof has at least upper and lower wedge-like steps taking the form of truncated pyramids, with the longitudinal axes thereof coinciding with the longitudinal axis of said rod, and with the apices facing said one rod end, whereas the other system includes wedge-like clamping jaws installed on the faces of said pyramids for their possible displacement therealong, to provide for their radial displacement in cross-sectional planes of the casing pipes, until said jaws rest against the inner surfaces of the pipes.

3. The equipment as defined in claim 2, wherein each face of at least one of said wedge-like steps has mounted thereon a pin-type detent provided with a spring and cooperating with a seat made in the corresponding one of said clamping jaws, located in the extreme upper position.

4. The equipment as defined in claim 2, wherein said wedge-like clamping jaws are displaced along guides made in said faces of the pyramids of each of said wedge-like steps.

5. The equipment as defined in claim 4, wherein the configuration of the working surfaces of said clamping jaws matches that of the inner surfaces of the casing pipes and has teeth directed perpendicular to the axes of the pipes.

6. The equipment as defined in claim 5, wherein said clamping jaws of each step, located vertically, above or below each other, are rigidly connected by mechanisms for adjusting their distances, to compensate for discrepancies encountered in the manufacture of said jaws and of said wedge-like steps of the rod.

7. The equipment as defined in claim 6, wherein said adjusting mechanism is in the form of two screws, one of them having a right-hand thread and being connected to one of said clamping jaws, while the other screw has a left-hand thread and is connected to an opposite jaw, said screws being interconnected by a correspondingly threaded nut.

8. The equipment as defined in claim 2, wherein said one end of the rod carries a sleeve installed for possible axial displacement and connected to each clamping jaw of said upper wedge-like steps by means of a two-link mechanism.

' 9. The equipment as defined in claim 8, wherein an outer surface of said sleeve is threaded and has a spacer nut mounted thereon, having a spherical surface.

10. The equipment as defined in claim 8, further comprising a lever installed on each clamping jaw of said upper wedge-like step by means of a hinge, with a spring for preliminary clamping of the casing pipes, said spacer nut having on the end thereof opposite to the joint of said lever a spherical rubbed surface facing the inner surfaces of the pipes, said jaw having a wedgelike surface cooperating with said spherical surface of the spacer nut. 

1. An equipment for resistance butt-welding of casing pipes above a well head into a casing string and subsequent running the string Into the well, comprising: a welding machine of the type adapted to pass through and installed in a stationary manner above the well; a grip to bring the pipes into said welding machine and to run a welded casing string into the well, located coaxially to said welding machine, a mechanism for vertical displacement of said grip along the axis of the well; said welding machine including mechanisms for clamping the ends of the pipes being welded, and a non-split housing embracing the string and connected to said clamping mechanism; said grip having maximum overall cross-section dimensions that do not exceed the outer diameters of the pipes, to permit the welded string to be lowered through said housing of the welding machine.
 2. The equipment as defined in claim 1, wherein said grip includes two systems positioned coaxially for possible relative displacement, one system representing a hollow rod connected to said displacement mechanism, whose one end has a cylindrical surface, while the other end thereof has at least upper and lower wedge-like steps taking the form of truncated pyramids, with the longitudinal axes thereof coinciding with the longitudinal axis of said rod, and with the apices facing said one rod end, whereas the other system includes wedge-like clamping jaws installed on the faces of said pyramids for their possible displacement therealong, to provide for their radial displacement in cross-sectional planes of the casing pipes, until said jaws rest against the inner surfaces of the pipes.
 3. The equipment as defined in claim 2, wherein each face of at least one of said wedge-like steps has mounted thereon a pin-type detent provided with a spring and cooperating with a seat made in the corresponding one of said clamping jaws, located in the extreme upper position.
 4. The equipment as defined in claim 2, wherein said wedge-like clamping jaws are displaced along guides made in said faces of the pyramids of each of said wedge-like steps.
 5. The equipment as defined in claim 4, wherein the configuration of the working surfaces of said clamping jaws matches that of the inner surfaces of the casing pipes and has teeth directed perpendicular to the axes of the pipes.
 6. The equipment as defined in claim 5, wherein said clamping jaws of each step, located vertically, above or below each other, are rigidly connected by mechanisms for adjusting their distances, to compensate for discrepancies encountered in the manufacture of said jaws and of said wedge-like steps of the rod.
 7. The equipment as defined in claim 6, wherein said adjusting mechanism is in the form of two screws, one of them having a right-hand thread and being connected to one of said clamping jaws, while the other screw has a left-hand thread and is connected to an opposite jaw, said screws being interconnected by a correspondingly threaded nut.
 8. The equipment as defined in claim 2, wherein said one end of the rod carries a sleeve installed for possible axial displacement and connected to each clamping jaw of said upper wedge-like steps by means of a two-link mechanism.
 9. The equipment as defined in claim 8, wherein an outer surface of said sleeve is threaded and has a spacer nut mounted thereon, having a spherical surface.
 10. The equipment as defined in claim 8, further comprising a lever installed on each clamping jaw of said upper wedge-like step by means of a hinge, with a spring for preliminary clamping of the casing pipes, said spacer nut having on the end thereof opposite to the joint of said lever a spherical rubbed surface facing the inner surfaces of the pipes, said jaw having a wedge-like surface cooperating with said spherical surface of the spacer nut. 